The specific objectives of this research are all related to our long-range goal of advancing the understanding of neural mechanisms of learning and memory. (1) Study of changes in brain anatomy and brain RNA/DNA induced by formal training in self-paced trials in mazes available 24 hr per day; the rats traverse the mazes to obtain food and water. (2) Recovery of problem-solving ability in rats after brain lesions is being studied as a function of postlesion environments (enriched, standard colony, or impoverished). Factors being studied include age at lesion, length of exposure to varied environments, and type of brain damage. (3) Further testing and extension of our findings concerning the role of protein synthesis in formation of long-term memory in mice. We have found evidence that, in the case of strong training, new messenger RNA is not required for such protein synthesis. We have also found that drugs that increase or decrease arousal shortly after training modify long-term memory although they affect protein synthesis only slightly. BIBLIOGRAPHIC REFERENCES: Bennett, E. L., Flood, J. F., Orme, A., Rosenzweig, M. R., & Jarvik, M. Minimum duration of protein synthesis needed to establish long-term memory. Fifth International Meeting of the ISN. Barcelona, Spain, 1975. Abstract. Rosenzweig, M. R., Will, B. E., & Bennett, E. L. Effects of enriched experience on recovery of rats from cortical lesions, problem-solving scores and brain measures. Society for Neuroscience, 5th Annual Meeting, 1975. Abstract, p. 508.